It is believed that one source of contamination in polymer product comes from polymer produced downstream of a polymerization reactor, under conditions (e.g., temperature, pressure, and/or monomer concentration) different from the controlled conditions of the polymerization reactor. Such contaminant polymers, produced under different conditions, typically have molecular weight and composition different than the bulk polymer produced in the intended polymerization reaction zone. It is hypothesized that these contaminant polymers are produced at least in part owing to still-active polymerization catalyst remaining in a polymerization effluent leaving the polymerization reactor. These contaminant polymers can cause many problems, such as fouling in the polymerization reactor system (particularly in conduits and units downstream of the reactor), or they can result in surface defects in products made from the polymer product. For instance, copolymer elastomers, such as ethylene-α-olefin-polyene elastomers (e.g., ethylene-propylene-diene or EPDM rubbers) may be formed into articles, such as extruded weatherseals. Such articles may contain areas of polymer with different physical properties from the bulk product, and manifest as a defect in the article.
Quenching agents are frequently added just downstream of a polymerization reaction zone in an attempt to address this problem. Quenching agents are compounds that react with polymerization catalysts so as to deactivate the catalysts, thereby halting undesired downstream polymerization reactions.
Some references of potential interest with regard to this problem include: U.S. Pat. Nos. 2,653,959; 2,943,105; 3,489,808; 3,931,350; 4,337,156; 5,245,107; 5,326,855; 5,427,689; 6,051,631; 6,111,162; 6,118,037; 6,632,766; 6,790,344; 6,987,152; 7,102,044; 7,141,630; 7,141,631; 7,326,821; 7,368,618; 7,576,248; and 9,382,344; U.S. Patent Application Publication Nos. 2002/147377; 2004/0254416; 2009/0312511; 2010/0197989; and 2011/0079145; European Patent Application Publication No. 1022056A; PCT Publication Nos. WO 2002/06188; WO 2004/033507; WO 2008/010962; WO 2008/013519; and WO 2009/010666; and Yu G. Osokin, 47, PETROLEUM CHEMISTRY, pp. 1-11 (2007), and 48, PETROLEUM CHEMISTRY, pp. 71-82 (2008).
However, quenching agents, particularly water, frequently fail to deactivate the polymerization catalyst quickly enough. Some degree of uncontrolled polymerization reactions still persist downstream of the polymerization reactor.